Investigating groundwater and surface water interactions using remote sensing, hydrochemistry, and stable isotopes in the Barotse Floodplain, Zambia

Groundwater and surface water are inseparably linked, thus the understanding of their interactions is indispensable toward developing effective conjunctive water resource management strategies, particularly for ecosystems, such as wetlands, which provide numerous ecosystem services. This study aimed to identify potential areas of Groundwater-surface water (GW-SW) interactions and mechanisms that facilitate them using remote sensing, hydrochemistry, and stable isotopes. The results of remote sensing analysis using Normalised Difference Vegetation Index (NDVI) show that the vegetation is sensitive to the dynamics of groundwater level, with shallower levels (<10 m) in the lower reaches compared to deeper levels (>10 m) in the upper catchment. The study postulates that the near surface groundwater level, maybe due to the near proximity river system (Zambezi River) losing water to recharge the aquifer system, compared to upstream which may be discharging to floodplains (gaining system). Using Hierarchical Cluster Analysis (HCA) of the hydrochemical data, surface, and groundwater showed three similarity clusters of hydrochemistry consisting of Ca-Mg-HCO3, Na-HCO3, and Na-Cl. These zones are further investigated and likely represent geological variability, aquifer confinement, and the degree of GW–SW interactions. The outcomes of this research provide critical input for integrated protection and conservation of ecosystem services in floodplain and aquifer systems.